Contemporary radio receiver systems often have an individual antenna dedicated to an individual receiver. This is one antenna-receiver relationship is not optimal when at a singular location multiple receivers must be used. For instance, in a vehicular application often a user will want to have and operate an AM/FM radio receiver, a cellular phone, a pager, a navigation receiver, a wireless remote entry system, and a security system. In some prior art systems the user would need a separate antenna for operating each receiver. This is particularly cumbersome, difficult to install, costly to vehicle manufacturers, and unsightly to vehicle users.
Some prior art vehicular systems shared a common antenna for more than one receiver, such as in the case of an AM radio receiver, an FM radio receiver, and a CB (Citizen's Band) receiver.
In a first shared antenna design scheme, all of the receivers, AM radio, FM radio, and CB, are simultaneously connected to the singular antenna at a common electrical connection. In this scheme the antenna-to-receiver matching for the individual receivers is compromise that relies on the separate, distal, frequency ranges of the complementary receivers to achieve (for each receiver) a less than optimal antenna-to-receiver matching. Note that matching refers to an impedance balance between the antenna and the coupled receiver. So the matching aspect of the design of the shared antenna-CB receiver coupling is affected by the also-connected shared antenna-FM receiver coupling, and the shared antenna-AM radio receiver coupling.
In another shared antenna design scheme, the user has to deliberately switch (choose) between the active receiver of the group of receivers. In one prior art scheme, when the user selects a receiver, the shared, or common, antenna is switched to the selected receiver and the antenna-to-receiver matching is optimized for that coupling. A singular receiver would then be connected to, and operating on a signal received from the common antenna. This can work when you know when to invoke the receiver and exclusively for a singular antenna-receiver coupling. This approach will not work for a queued receiver, such as a cellular phone, because the user would have to anticipate when a call came in to manually switch the antenna coupling to the cellular receiver. This is also the case in the other above-mentioned queued receivers such as the pager, navigation receiver, wireless remote entry system, and security system. Since services associated with these type of queued receivers are truly interrupt, or asynchronously queued it would be hard to imaging how a user could switch these receivers to a common antenna at the appropriate time. Furthermore, since this scheme inherently only supports a singular antenna-receiver coupling only one receiver can receive at a time using the common antenna.
Neither of the prior art approaches is satisfactory as the number and functional type of receivers and associated antennas increase.
What is needed is an improved antenna-receiver system that both minimizes the number of antennas, allows autonomously queued receivers to share a common antenna, and enables multi-listen or simultaneous reception using a shared antenna.